This application is directed to lubricant compositions containing small additive concentrations of alcoholic/dimercaptothiadiazole-derived hydroxy borates which possess excellent antioxidant properties as well as very good antiwear and extreme pressure/load carrying characteristics.
The use of alcoholic borate compositions such as borated alkane diols is well known for its friction-modifying properties in a variety of lubricant and grease application, e.g., U.S. Pat. No. 4,615,827.
The use of 2,5-dimercapto 1,3,4-thiadiazole and its derivatives has found widespread application as multifunctional lubricant anticorrosion, antiwear, antioxidant and copper passivation additives, see U.S. Pat. Nos. 4,661,273 and 4,584,114.
The use of borate esters has been widely reported as having beneficial multifunctional and friction reducing properties. For example borates and borate esters are disclosed in RE 37,295 and in U.S. Pat. Nos. 4,370,248; 4,298,486 and 4,273,665.
It has now been found that the use of alcoholic/dimercaptothiadiazole-derived hydroxy borates provides exceptional antioxidant coupled with very good antiwear/EP activity.